Acute lymphoblastic leukemia and Down syndrome: the collaborative study of the Tokyo Children’s Cancer Study Group and the Kyushu Yamaguchi Children’s Cancer Study Group

The Tokyo Children’s Cancer Study Group (TCCSG) and the Kyushu Yamaguchi Children’s Cancer Study Group (KYCCSG) performed a collaborative analysis of data on children with Down syndrome and acute lymphoblastic leukemia (DS-ALL). Among the 1,139 patients who were enrolled in the TCCSG L99-15, L99-1502, or the KYCCSG ALL 96 study, 13 patients with newly diagnosed ALL had DS. In the DS patients, a significantly higher proportion of patients developed ALL at age 5 years or older compared with the non-DS ALL patients (P < 0.001). The 5-year relapse-free or overall survival of DS-ALL patients was 50.0 or 61.5%, respectively. Relapse accounted for all causes of death. In the TCCSG L99-15 cohort, the overall survival of DS-ALL patients was 42.9%, which was significantly worse compared with 87.9% in the non-DS population (P < 0.001). The survival of patients who received reduced-dose chemotherapy was significantly worse than those who received full-dose chemotherapy (P < 0.001). However, a higher dose of methotrexate was not associated with a better outcome. Results of our preliminary study suggest that the survival of DS-ALL patients could be improved by treatment without dose reduction if possible, although the appropriate dose of methotrexate for DS-ALL needs to be determined.